Tired/missed period/not pregnant?

[ReturnofSaturn]

My period is a few days late. It is always usually pretty regular, on the same day every month.
Coincidentally for the last couple of weeks I have been feeling more tired than usual and a lack of energy.
I now also have a lack of appetite which is unusual for me.
Also burping and farting a lot but thats not that uncommon for me :).

Took a pregnancy test this morning, negative. I didn't think I would be though.

What could this be?
Iam 27 and otherwise in good health no conditions or medication etc

Thanks

[ReturnofSaturn]

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